Method of casting



Oct. 30, 1945. HJE. M WANE ET AL METHOD OF CASTING Filed Sept. 30, 1942swam Wow Patented Oct. 30, 1945 METHOD OF CASTING Henry E. McWane andHugh K. McGavocln Lynchburg, Va.; said McGavock asslgnor to said McWaneApplication September 30, 1942 Serial No. 460,259

4 Claims. ((122-290) The present invention relates to castingintroducing molten ferrous material into the casting cavities of chillmolds by means of top gating. This method is particularly adaptable incasting chilled articles such as plow points by means of controlledapparatus such as is disclosed in my co-pending application Serial No.460,566, filed Oct. 2, 1942. I

The use of top gating, especially in cooled metal molds, presentsseveral distinct advantages. First, it permits pouring at a lowertemperature than with bottom gating, allowing the casting to partiallyshrink as the mold is being filled, and thus minimizing the shrinkagestrains in the casting. Next, the use of a cooler metal, by hasteningthe time of solidification, will reduce the fin size on the casting.Another important advantage resulting from the use of top gating is thereduction of sprue loss. We have been able by our casting methods toreduce the sprue loss to about 5% whereas the loss resulting from theuse of conventional popring methods with bottom gating was approximately50% of the weight,

of the casting.

While it is admitted that top gating of molds is not new, considerabledifliculty has been encountered in the past in the production ofsatisfactory castings in permanent metal molds of liquid cooled type dueprimarily to conventional hand pouring from a foundry ladle with thenecessary use of a relatively hot metal and lack of control of the sizeand velocity and direction of the pouring stream. The metal wouldcontact the cold gate of the mold and freeze thereon, restricting andsometimes completely obstructing the gate. The use of gate liners of lowheat conductivity and other means have been tried to overcome thisfactor but to date we know of no remedy that has been attempted whichwill produce completely satisfactory castings.

It is therefore one of the principal objects of our invention toovercome the difilculties heretofore encountered in casting chilledarticles in top gated cooled molds.

Another important object of our invention is to provide a method ofcasting which so directs the stream of molten metal through the castingcavity of a cooled metal mold that the stream of molten metal itselfwill efiect the formation of gray iron in that portion of the castingdesired gray while the wearing portions will be highly chilled.

Yet another object is to provide a method of casting ferrous articles inmetal molds with to gating wherein the size of the stream of moltenmetal is controlled with respect to the gate size so that the moltenmetal is prevented from coming in contact with the gate.

Other objects and advantages will be apparent to those skilled in theart from the following description'and' by reference to the accompanyindrawing which forms a part thereof.

In the drawing, in which like characters of reference are employed todesignate like parts:

Figure 1 is a face view of one half of a permanent metal moldillustrating the flow of molten metal into the casting cavit thereoffrom a bottom pour ladle, a fragment of which is shown in transversesection, and

Figure 2 is a transverse sectional view taken along the line 2-2 lookingin the direction of the arrows and showing both halves of the mold 'inoperative position.

In carrying out our improved method of casting chilled articles wecontemplate the use of a liquid cooled mold having a top gate. The moldis positioned so that the gravity line of the metal being poured thereinwill coincide with the axis of the gate and correspond to that portionof the casting being produced which is desired to be gray. Preferablythe mold is positioned so that the molcn metal will initially contactthe lowest part of the casting cavity. A bottom pouring ladle, having apouring orifice of smaller cross sectional area than that of the gate,is employed for introducing the molten metal into the mold.

In the drawing we have shown a two part metal mold I having a castingcavity 2 formed in mold blocks 3 and 4 which are provided with waterjackets 5 and 6, respectively. Through these jackets is circulated acooling liquid 1 to which is transferred the heat of. the molten metalby means of the highly conductive blocks 3 and 4. A gate 8 is providedin the top of the mold to communicate with the casting cavity 2, andwhen the mold is in operative position will be preferably in a verticalline directly above the lowest part of the casting cavity. While othertypes of molds may be used, we have illustrated a mold for castingchilled plow points, our casting method being particularly adapted tothe production of this article.

Directly above the mold l is positioned a pouring ladle 9 of refractorymaterial and having a bowl Ill for the reception of a molten metal lland a pouring orifice l2 communicating with the bottom of the bowl. Thisorifice i2 is generally of similar cross section to the gate 8 but is ofsmaller size and when the parts are in pouring position has its axicoinciding with the axis of the gate. A reciprocatingstopper or plug i3is provided to open and close the orifice l2 and to regulate thevelocity of the pouring stream ll by means of the extent of its openingmovement.

In operation the parts are positioned as described above, molten metalis admitted to the bowl 10 of the pouring ladle 8 and the stopper I3 israised to allow the metal to flow through the orifice l2 and into thegate 8. The metal passes through the gate 8 without contacting its coolmetal walls, which would normally result in the metal freezing onto thegate, and then falls in a straight line to the lower portion l of thecasting cavity 2. Because of the definite control 01' the metal streamand the fact that the metal may be poured at a lower temperature thanwith hand pouring, it almost immediately solidifies with a hard whitestructure upon coming in contact with this portion of the cool moldcavity.

With continued pouring the metal rises to fill the cavity 2 flowing inall directions away from the stream l4. Since the cavity 2 iscomparatively thin, the stream of metal I4 will have the eilect ofpreheating the faces of the cavity which lie adjacent the path of thestream and this, together with the fact that heat of the pouring metalis conducted through a portion of the rising casting, the cool rate ofthis portion is sufliciently retarded to cause it to harden with a graystructure. This gray area we have indicated roughly as being within thedotted lines IS in Figure l. The portions of thecasting which will lieoutside this area, specifically the working edges of the plow point,because they are not 1.-

affected by the heat of the stream, will solidify white. The amount ofthis gray area maybe varied by increasing or decreasing the rate of flowof the metal from the ladle 9, obviously the slower the pouring rate thegreater the amount of heat radiated and conducted by the stream and thelarger the gray portion of the casting. This pouring rate may beaccurately controlled by the amount the stopper i3 is raised and theamount of opening of the orifice l2.

Thus it will be seen that by the combined use of controlled pouring andtop gating we are able to produce castings and particularly suchcastings as chilled plow points which have optimum workingcharacteristics. In addition, principally because of the low metal heatand slow pouring permitted by our methods, shrinkage has occurred in atleast a part of the casting before the mold has been completely filled,thereby practically eliminating the large sprues necessary in rapidpouring. Also, because of the above-fins and cracked castings, whichlatter are caused priflcipally by shrinkage strains set up in thecasting while within the mold, have been reduced to a minimum.

While only a preferred embodiment of our invention is herein shown anddescribed, it is to be understood that changes which will be obvious tothose skilled in the art may be made in the process, and the method maybe applied to the production of other articles than herein disclosedwithout departing from the spirit of the invention or the scope of theappended claims.

We claim:

1. A method of regulating the chill in comparatively thin gray castingsproduced in a metallic mold having a top gate comprising positioning themold so that the lowest portion of the mold cavity and the mold gate arealigned in the mean axis of that portion of the resulting castingdesired to be gray, introducing a stream of molten iron through the gateinto the mold cavity so that it initially contacts the lowest portion ofthe cavity, and controlling the rate of introduction of molten iron tocontrol the degree of preheating of the walls of the mold cavityadjacent said stream to thereby regulate the depth of chill of the grayportion of the casting.

2. A method of regulating the chill in comparatively thin gray ironcastings produced in a metallic mold having a top gate comprisingpositioning the mold so that the lowest portion of the mold cavity andthe mold gate are aligned in the means axis of that portion of theresulting casting desired to be gray, restricting a stream of molteniron to a size less than the size of the gate, introducing therestricted stream into the mold cavity so that it initially contacts thelowest portion of the cavity, and controlling the rate of introductionof molten iron to control the degree of preheating of the walls of themolten cavity adjacent said stream to thereby regulate the depth ofchill of the gray portion of the casting.

3. A method of regulating the chill in the casting of plow points in ametallic mold having a top gate comprising positioning the mold so thatthe lowest portion of the mold cavity which forms the tip of the plowpoint and the mold gate are aligned in the mean axis of the portion ofthe plow point desired to be gray, introducing a stream of molten ironinto the mold cavity so that it initially contacts the lowest portion ofthe cavity, and controlling the rate of introduction oi molten iron tocontrol the degree of preheating of the walls of the mold cavityadjacent said stream to thereby regulate the depth of chili of the grayportion.

4. A method of regulating the chill in the casting of plow points in ametallic mold having a top gate comprising positioning the mold so thatthe lowest portion of the mold cavity which forms the tip of the plowpoint and the mold gate are aligned in the mean axis of the portion ofthe plow point desired to be gray, restricting a stream mold cavityadjacent said stream to thereby regulate the depth of chill of the grayportion.

HENRY E. MCWANE. HUGH K. MoGAVOCK.

